1. Field of the Invention
The present invention relates to an ultrasonic motor and a manufacturing method thereof.
2. Description of Related Art
Various Langevin type ultrasonic motors, each of which has a generally cylindrical shape and generates a standing wave, have been known (e.g., one disclosed in U.S. Pat. No. 6,018,213 corresponding to Japanese Unexamined Patent Publication No. 11-155288). FIG. 8 shows an actuator having one previously proposed Langevin type ultrasonic motor. The previously proposed ultrasonic motor includes a stator 81 and a rotor 82. The stator 81 is formed into a generally cylindrical shape. Furthermore, the stator 81 includes an upper metal block 89, a first electrode plate 88, a first piezoelectric element 87, a second electrode plate 86, a second piezoelectric element 85, a third electrode plate 84 and a lower metal block 83, which are stacked in this order from top to bottom of the stator 81 and are fastened by a bolt 90 that extends therethrough. A plurality of slits 83a is formed in an outer peripheral surface of the lower metal block 83 in such a manner that the slits 83a are circumferentially arranged at generally equal angular intervals. The slits 83a generate a torsional vibration in response to a longitudinal vibration generated by the first and second piezoelectric elements 87, 85. The rotor 82 is formed into a generally cylindrical shape. The rotor 82 is urged against a top end surface of the stator 81, i.e., a top end surface of the upper mental block 89 by a Belleville spring 91.
When a high frequency voltage is applied to the first to third electrode plates 88, 86, 84, a longitudinal vibration is generated by the first and second piezoelectric elements 87, 85, and a torsional vibration is generated by the slits 83a in response to the longitudinal vibration. Thus, the rotor 82 is rotated by these vibrations.
In the previously proposed ultrasonic motor shown in FIG. 8, the first to third electrode plates 88, 86, 84, which are made of copper or its alloy, are used as conductive members that are electrically connected to the first and second piezoelectric elements 87, 85. The lower and upper metal blocks 83, 89 are made of aluminum or its alloy. In order to perform appropriate recycling of materials of the ultrasonic motor, the first to third electrode plates 88, 86, 84 (copper or its alloy) need to be removed from the stator 81 (aluminum or its alloy). However, in the stator 81, the first to third electrode plates 88, 86, 84 are fastened between the lower metal block 83 and the upper metal block 89, so that it is difficult to remove the first to third electrode plates 88, 86, 84 from the lower and upper metal blocks 83, 89, resulting in low recyclability of the materials.